The proposed research is designed to further our understanding of the cognitive and linguistic processes that underlie human language use. The major focus is on the organization of syntactic mechanisms in the production of speech. Little is currently known about these mechanisms despite their importance to human linguistic communication and to more general theories of complex cognitive skills. There are two central questions about the functions of syntax in speech that have to be addressed by a theory of language use. The first concerns the mapping from semantic to grammatical categories, and the second the nature of the processes that manipulate the elements of the syntactic vocabulary. For the purposes of this investigation, these questions are framed in terms of a theory that accords an important role to momentary changes in the accessibility of the elements and structures of language, over and above their semantic privileges or communicative valence. The hypotheses to be tested concern the locus of syntactic variations in sentences, the relationship between syntactic variations and features of the intended message, the nature of the linkage between underlying relational and superficial positional information in the production patterns of adults and children, the impact of rhythm and intonation on the creation of structure, and the role of working memory in the generation of sentence form. The long-term goal of the research program that motivates the experiments in this proposal is to explain the integration of linguistic information in speech. This integrative ability is a fundamental requirement of fluent, productive language use. Its absence is a prominent feature of a number of states and processes that have assumed great importance in the effort to explain human language, including the loss of linguistic abilities in aphasia and their acquisition in development. Better understanding of the higher level mechanisms of speech production will illuminate issues in these areas as well as in the normal adult use of language.